From patchwork Tue May 31 16:27:49 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dave Martin X-Patchwork-Id: 1682 Return-Path: Delivered-To: unknown Received: from imap.gmail.com (74.125.159.109) by localhost6.localdomain6 with IMAP4-SSL; 08 Jun 2011 14:54:21 -0000 Delivered-To: patches@linaro.org Received: by 10.52.110.9 with SMTP id hw9cs300121vdb; Tue, 31 May 2011 09:27:57 -0700 (PDT) Received: by 10.227.5.205 with SMTP id 13mr6148035wbw.31.1306859276845; Tue, 31 May 2011 09:27:56 -0700 (PDT) Received: from mail-wy0-f178.google.com (mail-wy0-f178.google.com [74.125.82.178]) by mx.google.com with ESMTPS id e7si520020wbh.139.2011.05.31.09.27.56 (version=TLSv1/SSLv3 cipher=OTHER); Tue, 31 May 2011 09:27:56 -0700 (PDT) Received-SPF: neutral (google.com: 74.125.82.178 is neither permitted nor denied by best guess record for domain of dave.martin@linaro.org) client-ip=74.125.82.178; Authentication-Results: mx.google.com; spf=neutral (google.com: 74.125.82.178 is neither permitted nor denied by best guess record for domain of dave.martin@linaro.org) smtp.mail=dave.martin@linaro.org Received: by mail-wy0-f178.google.com with SMTP id 33so4185880wyb.37 for ; Tue, 31 May 2011 09:27:56 -0700 (PDT) Received: by 10.227.176.136 with SMTP id be8mr2032803wbb.18.1306859275960; Tue, 31 May 2011 09:27:55 -0700 (PDT) Received: from e200948.peterhouse.linaro.org (fw-lnat.cambridge.arm.com [217.140.96.63]) by mx.google.com with ESMTPS id ge4sm154069wbb.13.2011.05.31.09.27.54 (version=SSLv3 cipher=OTHER); Tue, 31 May 2011 09:27:55 -0700 (PDT) From: Dave Martin To: linux-arm-kernel@lists.infradead.org Cc: patches@linaro.org, Catalin Marinas , Nicolas Pitre Subject: [PATCH REPOST] ARM: Thumb-2: Relax relocation requirements for non-function symbols Date: Tue, 31 May 2011 17:27:49 +0100 Message-Id: <1306859269-21304-1-git-send-email-dave.martin@linaro.org> X-Mailer: git-send-email 1.7.4.1 The "Thumb bit" of a symbol is only really meaningful for function symbols (STT_FUNC). However, sometimes a branch is relocated against a non-function symbol; for example, PC-relative branches to anonymous assembler local symbols are typically fixed up against the start-of-section symbol, which is not a function symbol. Some inline assembler generates references of this type, such as fixup code generated by macros in . The existing relocation code for R_ARM_THM_CALL/R_ARM_THM_JUMP24 interprets this case as an error, because the target symbol appears to be an ARM symbol; but this is really not the case, since the target symbol is just a base in these cases. The addend defines the precise offset to the target location, but since the addend is encoded in a non-interworking Thumb branch instruction, there is no explicit Thumb bit in the addend. Because these instructions never interwork, the implied Thumb bit in the addend is 1, and the destination is Thumb by definition. This patch removes the extraneous Thumb bit check for non-function symbols, enabling modules containing the affected relocation types to be loaded. No modification to the actual relocation code is required, since this code does not take bit[0] of the location->destination offset into account in any case. Function symbols are always checked for interworking conflicts, as before. Signed-off-by: Dave Martin Acked-by: Catalin Marinas --- [Reposting to give people a chance to comment.] arch/arm/kernel/module.c | 13 +++++++++++-- 1 files changed, 11 insertions(+), 2 deletions(-) diff --git a/arch/arm/kernel/module.c b/arch/arm/kernel/module.c index fee7c36..016d6a0 100644 --- a/arch/arm/kernel/module.c +++ b/arch/arm/kernel/module.c @@ -193,8 +193,17 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex, offset -= 0x02000000; offset += sym->st_value - loc; - /* only Thumb addresses allowed (no interworking) */ - if (!(offset & 1) || + /* + * For function symbols, only Thumb addresses are + * allowed (no interworking). + * + * For non-function symbols, the destination + * has no specific ARM/Thumb disposition, so + * the branch is resolved under the assumption + * that interworking is not required. + */ + if ((ELF32_ST_TYPE(sym->st_info) == STT_FUNC && + !(offset & 1)) || offset <= (s32)0xff000000 || offset >= (s32)0x01000000) { pr_err("%s: section %u reloc %u sym '%s': relocation %u out of range (%#lx -> %#x)\n",